1. Field of the Invention
The invention relates to genetic factors associated with sensitivity to chemotherapeutic drugs. More particularly, the invention relates to methods for identifying such factors as well as to uses for such factors.
2. Summary of the Related Art
A broad variety of chemotherapeutic agents are used in the treatment of human cancer. For example the textbook CANCER: Principles & Practice Of Oncology, 2d Edition, (De Vita et al., Eds.), J. B. Lippincott company, Philadelphia, Pa. (1985) discloses as major antineoplastic agents the plant alkaloids vincristine, vinblastine, vindesine, and VM-26; the antibiotics actinomycin-D, doxorubicin, daunorubicin, mithramycin, mitomycin C and bleomycin; the antimetabolites methotrexate, 5-fluorouracil, 5-fluorodeoxyuridine, 6-mercaptopurine, 6-thioguanine, cytosine arabinoside, 5-aza-cytidine and hydroxyurea; the alkylating agents cyclophosphamide, melphalan, busufan, CCNU, MeCCNU, BCNU, streptozotocin, chlorambucil, cis-diamminedichloroplatinum, azetidinylbenzoquinone; and the miscellaneous agents dacarbazine, mAMSA and mitoxantrone.
These and other chemotherapeutic agents such as etoposide and amsacrine have proven to be very useful in the treatment of cancer. Unfortunately, some tumor cells become resistant to specific chemotherapeutic agents, in some instances even to multiple chemotherapeutic agents. Such drug resistance or multiple drug resistance can theoretically arise from either the presence of genetic factors that confer resistance to the drugs, or from the absence of genetic factors that confer sensitivity to the drugs. The former type of factors have been identified, and include the multiple drug resistance gene mdr-1 (see Chen et al., Cell 47:381-389 (1986)). However, the latter type of factor remains largely unknown, perhaps in part because such absence of factors would tent to be a recessive trait.
Identification of genes associated with sensitivity to chemotherapeutic agents is desirable, because the discovery of such genes can lead to both diagnostic and therapeutic approaches for cancer cells and for drug resistant cancer cells, as well as to improvements in gene therapy and rational drug design. Recently, some developments have been made in the difficult area of isolating recessive genetic elements, including one involved in cytotoxic drug sensitivity. Roninson et al, U.S. Pat. No. 5,217,889 (Ser. No. 07/599,730 issued Jun. 8, 1993) teaches generalized method for obtaining genetic suppressor elements (GSEs), which are dominant negative factors that confer the recessive-type phenotype for the gene to which the particular GSE corresponds. (See also Holzmayer et al., Nucleic Acids Res. 20:711-717 (1992)). Gudkov et al., Proc. Natl. Acad. Sci. USA 90:3231-3235 (1993) teaches isolation of GSEs inducing resistance to topoisomerase II-interactive drugs from topoisomerase II cDNA. However, there remains a need for identifying yet unknown genes or genetic elements associated with sensitivity to chemotherapeutic agents, a task made more difficult by the unavailability of a cloned gene as starting material for preparing GSEs. Preferably, such genes or genetic elements will be involved in a common pathway that is implicated in sensitivity to more than one chemotherapeutic agent. Most preferably, such genes or genetic elements will be identified by direct selection of GSEs causing loss of the drug sensitivity phenotype.